Purification of synthetic alcohols



Patented Nov. 24, 1931 UNITE STATS JAMES RITCHIE PARK, or NOBTON-ON-TEES, ENGLAND, AssIenoR' To zit/Iranian CHEMICAL INDUSTRIES min, A conronarrron or GREAT en ra n. 1

PURIFICATION or sxnrnnrrc 'ALCOHOIJS No Drawing. Application filed October 13, 1930, Serial No. 488,558, at in Greatliritainneeember 19;}1929,

This invention relates to the purification of alcohols and more especially to the elimination of compounds of iron from alcohols obtained by synthesis from hydrogen and oxides of carbon.

Synthetic alcohols prepared by catalytic hydrogenation of oxides of carbon under pressure are often contaminated with iron compounds, e. g. iron carbonyl, which cannot be completely removed by simple distillation. lVith a View to the removal of small quantities of various undesired substances causing a peculiar unpleasant odor, it has already been proposed. to treat such synthetic alcohols, or a distillation fraction thereof, with an oxidizing agent, if desired with the addition of other purifying substances such as caustic soda solution, sodium bisulphite. or oxalic acid to the distilling liquid during the distillation.

According to the present invention crude synthetic alcohols of the kind described, or a distillation fraction thereof are subjected to a prolonged treatment with alkali for the purpose of eliminating iron compounds. Thus crude synthetic methanol, i. e, the condensate separating on cooling a gas mixture containing oxides of carbon and hydrogen which has been passed under pressure and at a suitable temperature over a methanol-' forming catalyst, may be mixed withsolid caustic soda and the mixture allowed to stand for several days at the ordinary temperature. If desired, the mixture may be maintained at a raised temperature, employing a reflux condenser if required, the necessary period of treatment being thereby diminished. lhe mixture, whether at the ordinary or a raised temperature, may be stirred during the treatment, and a slow current of air may be em ployed for this purpose. It may also be advantageous, especially when the mixture is allowed to stand at the ordinary temperature without subsequent stirring to aerate the mixture at the commencement of the treatment, e. g. by passing a current of air through the mixture, to ensure the presence of dissolved oxygen in the liquid, which is believed to play a part in the purification.

fter the prolonged treatment with alkali together with air over a roll of silver gauze ata red heat, as 1n formaldehyde manufacwilldgenerally :be to the mixture as such to. recovera product stantially free from iron, but this distillation be preceded by separation arm solid matter fromathe liquid, e, g. by.filtiatiori.v

Instead ofcausticsoda, other alkaline sub- I stances, e. g.--'potash or potassium or sodium carbonate, may be employed, desired in aqueous solution.

he vessels employed fon haudling thecrude andpure methanol may be made of mild steel as there is no, appreciable contamination of the methanol through contact with iron or steeL; I ,7 r

' Example-POM cubic metre of crude synthetic methanol, estimated to contain 130 liquid while filling, which occupied about 2 hours; The mixture was then allowed tostand at the ordinary temperature, without further supply of air, for 5 days." It was then distilled, the methanol obtained being estimated to contain not more than 2 parts of iron per thousand million.

The method ofestimating'the very small quantities of iron was to vaporize a known quantity of methanol and to pass the :vapors ture. The ironwas retained in the gauze and estimated by weighing the gauze before and after the passage of the vapors.

The methanol obtained{ according to the above example was especially suitable for the manufacture of formaldehyde by catalytic oxidation, using a silver gauze catalyst. The

use of crude methanol resulted in a relatively rapid deterioration of thecatalyst, while the methanol purified according to the example caused no appreciable loss of activity during an extended run. 7

Various changes may be made in the method described without departing from the the quantity inthe methanol used could be invention or sacrificing any of the advantages thereof.

Iclaim:

1. A process for the removal of iron compounds from crude synthetic alcohols, or distillation fractions thereof, prepared by catalytic hydrogenation of oxides of carbon, which includes the step of subjecting the impnre material to a prolonged treatment with alkali.

,2. A process for theremoval of iron compounds from crude synthetic alcohols, or V distillation fractions thereof, prepared by catalytic hydrogenation of oxides of carbon, 15 which comprises subjecting the impure material to a prolonged treatment with alkali and thereafier to distillation v I 3. A process as set forth in claim l'i-nfwh-ic'h abs-impure aicohol is allowed to stand for sereralrdays in the presence 05E caustic soda.

' -4.".'Aprocess=as"set forth i n cla-im 31in which "the mixture is stirred during the treatment.

5. A process assetforth in "claim 1 in which the mixture is stirred by a ctimntof-airduring ithetreatment.

6; A process "as set'forth in claim '1 in which the liquid is aerated a-t the-'com'meneementof the treatment and is 'th'en' allowed to stand.

y In testimon whereof, I-sfliX my signature.

' RITCHIE PARK.

as y 

